[flatsphere]

Hi there,

My wife has a 2005 Subaru Outback XT w/auto trans, about 135k miles. We live in SoCal.
The car runs great...well, most of the time. During the summer, or when driving up steep mountains with the AC running, the needle will climb steadily north towards overheating. Call me timid, but I've never been curious enough to find out what happens if I let the needle get into the red.
To let the needle drop, I have to turn the AC off. This isn't the best option now since we've been experiencing over a week of temperatures higher than 103.
I also noticed that the temp needle will drop to normal within a couple of minutes if I turn on the heater.

I did open the bonnet when we returned from a trip and with the car running, checked to make sure both fans were running. They were.

So guys, what do you think? We are a Subaru family, and love this car. We'd like to keep it running for many more years.

Cheers!
Rafael

 

[CSFiend]

Needs a radiator. Not a hard job.

 

[dryvby]

You may want to inspect the area in front of, and in between the radiator and the condenser core. It's probably clogged with dirt, leaves, etc. Spray it down with compressed air or flush the fins with water. Also, check that the seals on the undersides of the radiator caps are clean and smooth. A cooling flush may also be in order if its been a while.

 

[CSFiend]

A cooling flush may also be in order if its been a while.

Coolant system flushes are definitely a good maintenance practice, but in this case, a flush isn't going to help. As suggested, clean the area between the radiator and the condenser but if it's not packed solid, it won't make a difference.

I just dealt with the exact same symptoms, and replacing the radiator keeps my coolant temp right where it should be with the A/C on, even at 105* doing 80 MPH down in south TX.

 

[flatsphere]

Thanks guys! I'll check these things out over the weekend.

 

[Seabass]

Did you check the coolant level? Maybe you have a leak?

 

[flatsphere]

Coolant level is fine. I did replace the radiator, water pump and hoses last year as part of the 100k+ maintenance.
I took it to a mechanic and they ran it for an hour with the AC on. Didn't overheat, so they couldn't do anything.
So still getting very hot when running AC on very hot days (over 100 F) or when driving up the mountain.

 

[CSFiend]

Coolant level is fine. I did replace the radiator, water pump and hoses last year as part of the 100k+ maintenance.
I took it to a mechanic and they ran it for an hour with the AC on. Didn't overheat, so they couldn't do anything.
So still getting very hot when running AC on very hot days (over 100 F) or when driving up the mountain.

Did the mechanic drive it and attempt to simulate the conditions when the problem occurs, or just let it idle in the shop? Those are two completely different scenarios.

At speed, the engine is working hard. It's getting hot. Then, it has to deal with the extra hot air coming through the radiator from the condenser. If the radiator is clogged, it won't be able to deal with dissipating the extra heat from the condenser.

Is the radiator still under warranty? If it only overheats when on the road, at speed, under load... the radiator isn't working properly.

 

[tdelker]

You mention replacing the water pump. Could there be a connection? Did you use OEM thermostat? Often the advice is that aftermarket thermostats are should be avoided, although I don't see a reason given. Maybe someone put too much goop sealing the housing and restricted flow? What about a bad purge with air caught in the system? I seem to recall that a vacuum refill is highly suggested, rather than just running it to clear out trapped air pockets.

Just giving some other ideas...

Tom